C.D.S. - SIMBAD4 rel 1.7 - 2021.03.04CET19:45:42

2009A&A...493..671F - Astronomy and Astrophysics, volume 493, 671-676 (2009/1-2)

Bulk composition of the transiting hot Neptune around GJ436.


Abstract (from CDS):

The hot Neptune orbiting around GJ436 is a unique example of an intermediate mass planet. Its close-in orbit suggests that the planet has undergone migration and its study is fundamental to understand planet formation and evolution. As it transits its parent star, it is the only Neptune-mass extrasolar planet of known mass and radius, being slightly larger and more massive than Neptune (M=22.6M, R=4.19R). In this regime, several bulk compositions are possible: from an Earth-like core with a thick hydrogen envelope to a water-rich planet with a thin hydrogen envelope, and comprising a Neptune-like structure. We combine planet-structure modelling with an advanced planet-formation model to assess the likelihood of the different possible bulk compositions of GJ436b. We find that both an envelope-free water planet (``Ocean planet'') as well as a diminute version of a gaseous giant planet are excluded. Consisting of a rocky core with a thick hydrogen/helium envelope, a ``dry'' composition produces not only too small a radius but is also a very unlikely outcome of planet formation around such a low-mass star. We conclude that GJ436b is probably of much higher rock content than Neptune (more than 45% in mass), with a small H-He envelope (10-20% in mass). This is the expected outcome of the gathering of materials during the migration process in the inner disk, creating a population of which the hot Neptune is representative.

Abstract Copyright:

Journal keyword(s): planetary systems - planetary systems: formation - stars: individual: GJ436

Simbad objects: 3

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Number of rows : 3

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 Ross 905b Pl 11 42 11.0933874353 +26 42 23.658083337           ~ 637 1
2 Ross 905 PM* 11 42 11.0933874353 +26 42 23.658083337   12.06 10.613 10.272 8.24 M3V 518 1
3 HD 209458b Pl 22 03 10.7729598762 +18 53 03.548248479           ~ 1550 1

    Equat.    Gal    SGal    Ecl

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